The present invention relates to a copying apparatus which develops electrostatic latent images by means of a developing device, more specifically to a copying apparatus provided with a developing device which supplies a developer through the rotation of a developing roller.
Conventionally, an electrostatic copying machine performs monochrome copying operation using a black color. Therefore, if a typescript to be copied includes words underlined in, for example, red ink for attention, the underline cannot help being copied in the same black color of the typewritten words. Thus, those words which are set off by the red underline in the original document may hardly be able to be distinguished from other parts or words, and may fail to attract a reader's special attention in a copy. For the copying of such a two-color original document, it may be possible to use a multicolor electrostatic copying machine that has recently been developed. The copying machine of this type, however, is too expensive to enjoy reasonable running cost per copy. Moreover, it is uneconomical to use a multicolor copying machine for only two-color copying. Accordingly, there has conventionally been an increasing demand for a two-color electrostatic copying machine of a simple construction, more specifically an electrostatic copying apparatus for two-color copying using a black color and another.
Namely, there has been a demand for a simple construction copying apparatus capable of at least two different types of copying operations.